Yak 9u is the only fighter I fly anymore. 7 kills is my best in it without reloading.
It's an amazingly capable plane with a ton of strengths. The weakness being the armament and ammo loadout, I generally rtb'd in other rides with the ammo loadout the yak 'starts' with.
3 kills is pretty common before rtb'ing
It's a small target and very slippery, rolling scissors seem to work exceedingly well to displace those who find their way to your tail.
accelleration up the wazoo, this can be used in stall fighting as it recovers very quickly. I dont recall spits being a huge problem, I get as many of those as any other plane, that can be as much relative ability as anything tho.
Escapability / survivability. It can get out of bad situations very easily.
I believe the la7 is a tiny bit faster, I've run them down before, but I generally have a bit more e comming into the chase. However the yak owns the LA if he decides to fight.
Visibility. Great views, lotta freedom in the cockpit to customize the setup.